As is well known, many information disc apparatus for recording or reproducing optical information on or from an optical information disc, using a laser light which is generated from a semiconductor laser, have been developed.
In the optical information discs make for use in the many information disc apparatus available there is a standard provided in relation to preformat data. These data are pre-recorded by the disc manufacturer onto the disc to indicate various information such as characteristics associated with the disc.
Referring to FIG. 1, according to the standard the preformat data are recorded on an information disc 1 at a specific area 1b separated inwardly from a data area 1a which is provided for disc users to record or read optical information on or from the information disc 1. The area 1b of the preformat data is referred to an address area. Furthermore, the preformat data are recorded in the form of bar codes. One segment of the bar code comprises a plurality of pit trains which are arranged parallel in the range 29.0 to 29.3 cm from the center of the optical information disc 1 (see FIG. 2).
Typically, three sectors of the bar codes are allocated within a circle of the address area. Two neighboring sectors of the bar codes are separated from each other by a relatively long gap. Here the gap between the sectors of the bar codes will be referred to as an inter-sector gap. However, each segment of the bar code is also separated from the others in the same sector of the bar code by a relatively long gap. Here the gap between the segments of the bar code will be referred to as an inter-segment gap.
The inter-sector gap is usually designed to be longer than the inter-segment gap. However, both the inter-sector and inter-segment gaps are extremely large in comparison to gaps between pits in the pit trains. In other words, there is not much to choose between the inter-sector and inter-segment gaps when compared to the gap between the pits. Here the gap between the pits will be referred to as an inter-pit gap.
Thus, it was very difficult to distinguish between the inter-sector and inter-segment gaps. This frequently causes the conventional information disc apparatus to fail to properly read the sectors of the bar codes.